> They say the boiler is 84% efficient in converting electricity into hot water, and another 12% of waste heat is recycled, giving a total efficiency of 96%.
An electric water heater is 100% efficient.
An electric water heater is 100% efficient.
However, the USP of this product is that it's a drop-in replacement for existing gas boilers which are prevalent in some parts of the world. The article says the unit costs around £3,500 and installation of a replacement gas boiler costs around £500, so maybe ~£4,000 to switch from gas to electric. An equivalent air-source heat pump installation could easily cost £12,000, and often gas boilers are located in areas which are space-constrained.
I have a gas instant hot water heater, with a water softener it basically never builds up scale, otherwise a yearly acid flush is recommended and it has flush port that make it a easy job.
Most homes have one already in fact, as a backup for when the boiler breaks.
What will make the difference to all this is the combination of increased efficiency plus production at scale that makes retrofitting attractive to homeowners. Part of that scale could come from mandatory fitting of such equipment to all new builds.
And when talking about efficiency you must specify context. In this case heating water via electricity, not losses of storing the heated water which is a separate issue based on tank vs instant regardless of heating method.
Both systems are 100% efficient at turning electricity into heat. Neither system is 100% efficient at turning electricity into useful hot water. There are always losses. They're just being honest with their accounting.
Whats the point then? A resistive element immersed in water converts nearly 100% (probably some light losses at the elements base) of the energy to heat in the water its immersed in.
So on one hand you have complicated expensive microwave system that still resistively heats the water in a much more complicated way losing 4% still to waste heat or you have a much more simple resistive heating system that probably does better.
If this microwave tech has a COP of less than 1 (meaning it doesn't generate more thermal heating than you put in), then it doesn't solve this problem and better than resistive electric heating. You have the same electrical installation problems.
There may be some other advantage here (long-term maintenance?), but not power efficiency. Thermodynamics says so.
The only way to do better is to make something else colder while you heat your house, using some kind of heat pump.